Temperance

Temperance Lake is a 176-acre lake located just east of the City of Sherburn in Martin County. Temperance Lake is shallow, having a maximum depth of 5 ft. Due to its shallowness, the lake is prone to low oxygen levels in the winter. The last recorded low oxygen event occurred during the winter of 2018-2019; however, it was determined that the low oxygen had minimal effects on the fish population. Although Temperance Lake is located near headwaters of the watershed, the water quality during the survey is typically poor. The poor water quality is likely a result of nutrient runoff from nearby agricultural fields, resuspension of sediment from common carp, and mixing of the lake bottom by wind events. The virtually unlimited nutrient supply provides an environment in which microscopic organisms, like algae, can thrive resulting in extreme algae blooms. Temperance Lake is managed primarily for Northern Pike and secondarily for Yellow Perch. A Standard Survey was conducted during the week of June 17, 2025, to monitor fish populations using one gill net and nine trap nets. Catch rates of northern pike have varied greatly in Temperance Lake, ranging from 0 per gill net (2001, 2007, and 2019) to 48.5 per gill net (1991) and from 0.3 per trap net (2019) to 17.6 per trap net (1991). Record high catch rates were observed in 1991, the result of a very successful naturally reproduced year class. The 2025 trap net catch rate increased from the previous survey in 2019, increasing from 0.3 per trap net to 0.9 per trap net. Northern Pike range in length from 13.7 to 22.4 inches and averaged 15.8 inches in trap nets in 2025. The Northern Pike in Temperance Lake are likely fish that were stocked in 2024; however, natural reproduction has been documented in previous years, making it a possibility that they are naturally spawned fish. The availability of Northern Pike spawning habitat is often influenced by the amount of precipitation each year. Successful spawning is likely limited to years with above average precipitation when water levels are high enough to inundate vegetation to successfully spawn. The current stocking regime appears to be effective at providing a fishable Northern Pike population. Gill net catch rates of Yellow Perch in Temperance Lake have been highly variable, ranging from 29.0 per gill net in 2013 to 348.0 per gill net in 2019 and averaging 145.0 per gill net since 1991. In 2025, the catch rate of Yellow Perch was 183.0 per gill net and ranged in length from 0.7 to 12.2 inches and averaged 7.9 inches in the gill nets and 7.6 inches in the trap nets. The size range of Yellow Perch is perfect for anglers, especially over the next year or two as the maximum size of the largest fish increases. With many Yellow Perch in the lake there is a potential that harvest could occur to improve fishing on other local lakes. Harvest will also have the potential to increase growth by decreasing the population size and competition for limited food. OTHER SPECIES Other species sampled in 2025 were Bigmouth Buffalo, Black Bullhead, Common Carp, Green Sunfish, Largemouth Bass, Orangespotted Sunfish, White Sucker, and Yellow Bullhead. Black Bullhead ranged in length from 4.7 inches to 12.4 inches and averaged 8.9 inches in the gill net sample indicating they may be large enough for anglers to target. Bigmouth Buffalo were caught at a rate higher than their expected ranges. Bigmouth Buffalo, along with Common Carp, can negatively impact lakes when they are at high abundance by suspending sediment that has a high amount of nutrients and chemicals that negatively impact water quality.

A targeted survey of nearshore fish species in Temperance Lake was conducted on June 17-18, 2025, by Lake Biological Monitoring and Assessment (LBMA) program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing was completed at ten sampling stations. Similarly, a 50-foot seine was used to sample nine stations. One station was not seined due to soft substrate. Nearshore sampling captured eight species of fish, including six species that are tolerant of disturbance (i.e., Bigmouth Buffalo, Black Bullhead, Common Carp, Fathead Minnow, Green Sunfish, and Orangespotted Sunfish). However, zero species that are intolerant of disturbance were sampled. A summer trap and gill net survey was also conducted on June 9-10, 2025, by LBMA program staff. Nine trap nets were set along the shoreline in locations that encompassed multiple habitat types. Trap net sampling captured ten species of fish, including five species that are tolerant of disturbance (i.e., Bigmouth Buffalo, Black Bullhead, Common Carp, Green Sunfish, and Orangespotted Sunfish). Yellow Perch and Black Bullhead comprised a majority of the catch by number, whereas Bigmouth Buffalo and Yellow Perch comprised a majority by biomass. One gill net was set in the open water portion of the lake. Gill net sampling captured six species of fish, including four species that are tolerant of disturbance (i.e., Black Bullhead, Common Carp, Bigmouth Buffalo, and Orangespotted Sunfish). Yellow Perch comprised a majority of the catch by number, whereas Bigmouth Buffalo comprised a majority by biomass. Zero species that are intolerant of disturbance were sampled in the trap nets or gill nets. The nearshore, trap net, and gill net surveys were combined to describe the fish community and provide a fish-based index of biological integrity (FIBI) score. The FIBI uses fish community data to measure a lake's health, and the types of fish species present can help identify any stressors that may be negatively affecting the lake environment. In Minnesota lakes, certain fish species cannot survive without clean water and a healthy habitat (e.g., Banded Killifish, Iowa Darter, and Rock Bass), while other species are tolerant of degraded conditions (e.g., Orangespotted Sunfish and Common Carp). The FIBI score, composed of several fish community diversity and composition metrics, indicates the overall health of a lake by comparing it to what is expected for a healthy lake. For additional information on the FIBI, search for "lake index of biological integrity" on the mndnr.gov website. Results from this survey provide evidence that the fish community in Temperance Lake is adversely impacted by stressors, as indicated by an FIBI score below the general use impairment threshold for aquatic life use determined for similar lakes. These results are similar to previous findings, which indicated that Temperance Lake is impaired for biological health. The survey results will be considered when the biological health of the lake is assessed during the East Fork Des Moines River Watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. Maintaining natural shoreline buffers and implementing best management practices within the watershed, such as cover crops, no-till farming, buffer strips, targeted fertilizer application, and reduced tiling, are critical steps for reducing runoff and nutrients from entering the lake. These efforts are essential for improving the biological integrity of the lake and protecting its fish community for the future.

INTRODUCTION Temperance Lake is a 176-acre lake located just east of the City of Sherburn in Martin County. Temperance Lake is shallow lake, having a maximum depth of 5 ft. Due to its shallowness, the lake is prone to low oxygen levels in the winter. The last recorded low oxygen event occurred during the winter of 2018-2019; however, it was determined that the low oxygen had minimal effects on the fish population. Although Temperance Lake is located near the headwaters of the watershed, the water quality during the survey was poor as the water clarity was only 0.6 ft. The poor water quality is likely a result of nutrient runoff from nearby agricultural fields, stirring of sediment from common carp, and mixing of the lake bottom by wind events. The virtually unlimited nutrient supply provides an environment in which microscopic organisms, like algae, can thrive resulting in extreme algae blooms. Temperance Lake is managed for Northern Pike and Yellow Perch. Northern pike are stocked at a rate of 20 fingerlings per acre once every three years and have been stocked in 2005, 2008, and 2011. No Northern Pike were stocked in 2014 or 2017 due to low production of fingerlings in rearing ponds and a high population in the 2013 survey. A population assessment was conducted during the week of August 19, 2019 to monitor fish populations using 1 gill net and 6 trap nets. NORTHERN PIKE Catch rates of northern pike fluctuate a lot in Temperance Lake, ranging from 0 per gill net in 2019 to 48.5 per gill net in 1991. Record high catch rates were observed in 1991, the result of a naturally reproduced year class. The 2019 trap net catch rate was down from the previous survey in 2013, decreasing from 5.2 per trap net to 0.3 per trap net. Size structure of trap netted northern pike favored larger fish, as the 2 fish were 27.6 and 27.8 inches. The northern pike in Temperance Lake are likely fish that were stocked in 2011; however, natural reproduction has been documented in previous years, making it a possibility that they are naturally spawned fish. The availability of northern pike spawning habitat is often influenced by the amount of precipitation that floods plants near shore for fish to spawn in towards the end of March or beginning of April. The current stocking is maintaining some Northern Pike in the lake, but stocking will be used to boost the population. Northern Pike fingerling will be stocked in 2020 to help increase the population provided the rearing ponds produce. YELLOW PERCH Gill net catch rates of Yellow Perch in Temperance Lake have been up and down, ranging from 29 per gill net in 2013 to 348 per gill net in 2019. In 2019, the catch rate of Yellow Perch was 348 per gill net, which is the highest gill net catch for Temperance Lake. This comes after the 2013 survey which had the lowest catch rate. Size of the Yellow Perch was above average for southwest Minnesota. Yellow perch ranged in length from just over 5.5 inches to just shy of 10.5 inches and they averaged 7.5 inches. The size range of Yellow Perch is perfect for anglers, especially over the next year or two as they grow. Yellow perch were plump indicating they are finding adequate food. Angling for Yellow Perch should be good, if and when they bite, over the next few years. OTHER SPECIES Other species sampled in 2019 were Bigmouth Buffalo, Black Bullhead, Common Carp, Green Sunfish, Orangespotted Sunfish, White Sucker, and Yellow Bullhead. Black Bullhead, Common Carp, and White Sucker were caught within the expected catch rate ranges. Black Bullhead ranged in length from just over 6.5 inches to just shy of 11 inches and averaged nearly 9.5 inches indicating they may be large enough to target by anglers looking for some Black Bullhead to eat. Bigmouth Buffalo were caught slightly more than the expected catch rate range. Bigmouth Buffalo, along with Common Carp, can negatively impact lakes when they are at high abundance by suspending sediment that muddies the water with nutrients and chemicals that negatively impact water quality. Only 1 Green Sunfish and 4 Orangespotted Sunfish were caught, so not much can be said about them. They are typically found in and around rocks near shore if anglers wish to target Green Sunfish and Orangespotted Sunfish. SUMMARY Overall, Temperance Lake is typical of what is seen in southwest Minnesota when the lake is highly degraded and extremely shallow. The DNR often sees highs and lows in gamefish populations in these lakes, which is limited to Northern Pike and Yellow Perch for Temperance Lake. The DNR also observes undesirable species like Common Carp, Bigmouth Buffalo, and Black Bullhead dominating the fish community. Those three species together in Temperance Lake made up 53% of the gill net sample and 65% of the trap net sample by weight. On a positive note, Northern Pike and Yellow Perch tend to do well in shallow prairie lakes that are susceptible to low dissolved oxygen in the winter, like Temperance Lake. It appears that the Northern Pike and particularly the Yellow Perch populations are doing well and will provide a great angling opportunity over the next few years.

Based on Minnesota DNR survey data, anglers target Yellow Perch, Black Crappie, Largemouth Bass, White Crappie, and Pumpkinseed in Temperance. See the full species list above for catch rates, size structure, and quality scores.

We don't have a confirmed public access point on record for Temperance. Check the DNR LakeFinder page for current access details before you go.

Temperance has a maximum depth of 5 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Temperance is from 2025.

No invasive species are on record for Temperance in Minnesota DNR data. Always clean, drain, and dry your equipment to help keep it that way.